This invention relates to immunoglobulin products that bind with specificity to A33 antigen. In particular this invention is directed to A33 antigen specific CDRs. The antibodies and antibody like proteins may be humanized.
Use of antibodies as therapeutic agents is gaining acceptance as an important and valuable approach in the treatment of various conditions, such as types of cancer. The specificity of antibodies makes them particularly useful in treating conditions where a xe2x80x9cmarkerxe2x80x9d or xe2x80x9cmarkersxe2x80x9d characterize abnormal cells. Antibodies effectively target such cells by binding to these markers, which are molecules present in, or preferably on, the cell type of interest.
Initial forays into the production of antibodies used mice as subject animals. To summarize, mice were injected with the molecule of interest. As this molecule was foreign to the mouse, an antibody response would result. The antibodies were then purified from murine blood or serum, for eventual diagnostic or therapeutic use.
In vivo use of murine antibodies has been curtailed, however, for a number of reasons. Murine antibodies, recognized as foreign by a human host, elicit the so-called xe2x80x9chuman anti-mouse antibodyxe2x80x9d or xe2x80x9cHAMAxe2x80x9d response. See, e.g., Schiff, et al., Canc. Res. 45:879-885 (1985). In addition, the Fc portion of murine antibodies is not as efficacious in stimulating human complement or cell mediated toxicity.
There have been extensive and intensive efforts to circumvent such problems. One such approach is the development of chimeric antibodies. See, e.g., European Patent Applications 120694 and 125023 disclosing the general approach. Chimeric antibodies contain portions of antibodies from two or more different species, such as the variable regions of a mouse antibody, and the constant regions of a human antibody. The advantage of such chimeras is that they retain the specificity of murine antibodies, but also stimulate human Fc complement fixation. Such chimeras can still elicit a HAMA response, however. See, e.g., Bruggemann, et al., J. Exp. Med 170:2153-2157 (1989).
Additional approaches have been sought which would alleviate these problems. British Patent Application GB 2188638A and U.S. Pat. No. 5,585,089 are exemplary of technology in this area. These references disclose processes wherein recombinant antibodies are produced where the only portion of the antibody that is substituted is the complementarity determining region, or xe2x80x9cCDR.xe2x80x9d The CDR grafting technique has been used to generate antibodies which consist of murine CDRs, and human variable region framework and constant regions. See, e.g., Riechmann, et al., Nature 332:323-327 (1988), for teachings relating to such xe2x80x9chumanizedxe2x80x9d antibodies. These antibodies retain the human constant regions that are necessary for Fc dependent effector function, but are much less likely to evoke a HAMA response.
Substitution of murine CDRs for human CDRs is not generally sufficient to generate an efficacies humanized antibody. The humanized antibodies must include a small number of critical murine antibody residues in the human variable region. The particular residues of importance depend upon the structure of both the murine antibody and human antibody. See, e.g., WO 04381 to Harris et al. (2000).
Notwithstanding these issues, humanized antibodies have become much more available, as is evidenced by, e.g., U.S. Pat. No. 5,952,484 to Wallace et al. and U.S. Pat. No. 5,958,412 to Welt et al., both of which are incorporated by reference.
U.S. Pat. No. 5,958,412 describes humanized antibodies to a molecule referred to as xe2x80x9cA33.xe2x80x9d This molecule is known to be associated with colon cancer. See, e.g., U.S. Pat. Nos. 5,643,550 and 5,160,723, incorporated by reference. Also see U.S. Pat. No. 5,712,369, to Old, et al., also incorporated by reference, teaching the isolation and characterization of the A33 molecule.
Phage display is a methodology which has been used to express and to select recombinant antibodies. See, e.g., Vaughan, et al., Nat. Biotechnol. 16(6):535-539 (1998), incorporated by reference. This methodology is employed in the disclosure which follows.
The rabbit Ig gene repertoire has been well characterized. See, e.g., Knight, et al., Adv. Immunol 56:179-218 (1994). This characterization has permitted selection of monoclonal antibodies, by screening combinatorial antibody libraries displayed on phage (Ridder, et al., Biotechnology95(15):8910-15(1998). This information, together with information discussed infra, has been used to develop the invention described herein.
The structure of an immunoglobulin is discussed in standard textbooks such as Paul, W. E, Fundamental Immunology, Raven Press, New York, N.Y., 1993. Incorporated herein by reference.